Three equal resistors connected in series across a source of emf of negligible internal resistance together dissipate 10 W of power. What would be the power dissipated if the resistors are connected in parallel across the same source of e.m.f.

Explanation

Given three resistors are connected in series
i.e., `R_(s)=3R`
Also given, power dissipation P =10 W
i.e., `10=(v^(2))/(R_(s))` here V=E , r=0
i.e., `V^(2)=10xx3R` …..(1)
For parallel combination `R_(p)=(R/3)` so that
`p.=(V^(2))/(R_(p))=(3V^(2))/R`
i.e., p. =3(10) = 30 W